The described invention relates in general to surgical systems, devices, and methods and more specifically to an annuloplasty system for damaged heart valve repair. This invention is useful for humans and may be used for the surgical correction of a deformed heart valve, and in particular a heart valve that has become dilated.
Diseases of the mitral valve affect the annulus, altering annular geometry and function. Dilation and/or deformation of the valve annulus result in the displacement of the cusps away from the center of the valve. This results in an ineffective closure of the valve during ventricular contraction, which results in the regurgitation or leakage of blood during ventricle contraction.
Two known surgical methods or techniques, generally referred to as annuloplasty, are typically used to reshape the distended and/or deformed valve annulus. In the technique known as “plication”, the circumference of the valve annulus is reduced by implanting a prosthetic ring of reduced circumference about the base of the annulus while the annulus is pleated to reduce its circumference to that of the ring. In the technique known as “reconstruction”, the circumference of the annulus is not reduced, but the annulus is restructured into an elongate shape. To accomplish this goal, a rigid or semi-rigid ring (e.g., the Carpentier ring) having the same circumference as the annulus but in an elliptical shape is surgically implanted about the base of the valve. Both plication and restructuring are intended to eliminate the gap in the closure of the distended valve by bringing back together the tips of the valve cusps, reinforce suture lines, and prevent further annular dilatation.
Interrupted sutures of 2/0 braided synthetic material with double-end needles are typically used for the described surgical methods. The stitches are placed into the fibrous tissue of the annulus. Large bites of the heart annulus are taken, and the needles are passed close together through the ring prosthesis. The annuloplasty ring is slid down over the sutures into position above the mitral valve and the sutures are tied firmly, attaching the device to the annulus. As the sutures are tied down to approximate the prosthetic ring to the mitral valve annulus, the annular diameter is reduced and the contour is improved.
A hypothetically “ideal” annuloplasty would correct the dilatation of the posterior annulus in a measured fashion while allowing a full range of motion of the mitral annulus. Initially the prostheses were designed as rigid and flat frame members, to correct the dilation and reshape the valve annulus to the natural state. However, rigidity impedes the beneficial flexing movements and displacements of the native annulus during the cardiac cycle. Another disadvantage with highly rigid ring prosthesis is the tendency of the sutures to tear during the normal movement of the valve annulus.
Recognizing that the annulus is a dynamic structure that changes dramatically with the cardiac cycle, thereby facilitating a reduction in mitral orifice size to allow leaflet apposition, flexible annuloplasty rings have been developed. Flexible annuloplasty rings (e.g., the Duran ring) have been shown to minimize risk of dehiscence because there is reduced tension on sutures and reduced negative consequences of inaccurate placement of ring sutures. However, one disadvantage of the completely flexible ring prostheses is that during the implantation process the drawstring effect of the sutures tends to bunch the material covering the flexible ring at localized areas. The rigidity of the Carpentier ring prevents deformity, whereas when the Duran flexible ring is sutured to the annulus by interrupted U-stitches multiple plications of the Dacron polyester fabric occur. This bunching of the prosthesis resulted in the phenomenon known as multiple plications of the ring prosthesis. One result of this phenomenon is variability of the ability of the ring to control the shape of the valve annulus. Each plication of the posterior annulus is dependent on the tension placed on the sutures at the time of tying. Therefore, it is possible to have too small a plication resulting in insufficiency or too large a plication resulting in valve stenosis. Plication of the annuloplasty ring determines a reduction of at least one or two sizes in the selected flexible ring. The residual stenotic effect without early homodynamic repercussion, together with progression of the underlying disease, may be a predisposing factor toward valve stenosis necessitating late reoperation. Some patients in whom the Duran flexible ring had been inserted required valve-related operations as a result of hemolysis with or without prosthetic dehiscence. Patients who underwent reoperation for mitral restenosis showed absence of endothelium in the areas in which the ring was folded. In series of 85 patients reviewed after 10 to 12 years, Duran and coauthors (Duran CG, J L Pomar and J M Revuelta et al., Conservative operation for mitral insufficiency, J Thorac Cardiovasc Surg 79 (1980), pp. 326-337) found a 20.1% incidence of thromboembolic complications. The over narrowing and purse-string effects with irregular contour of the totally flexible ring were the main causes of high rate of thromboembolism.
While rigid and semi-rigid annuloplasty rings eliminate the bunching caused by flexible rings, the restrictive nature of such rings is generally detrimental to the valve's ability to open and close normally. On the other hand, because of their flexibility, flexible rings can be difficult to handle during surgical manipulations and generally must be supported during implantation by a holder, which is subsequently removed before tying off the implanting sutures. The Cosgrove Band is totally flexible; however, bunching of the Cosgrove Band is prevented by the suturing of the device on a rigid template subsequently removed after the implanting sutures are tied off. The approach of tying down over a rigid template eliminates the potential of plication of an inappropriate amount of the posterior annulus of the heart.
The rigid template is in turn releasably secured to a bendable handle to facilitate positioning of the template and ring in the heart adjacent to the annulus of the valve to be repaired. Once the template is placed and sutures initiated, the handle is withdrawn to give the surgeon room to work and properly see the annulus. When the procedure is completed, valve closure is tested by injecting saline solution. The sutures attaching the ring to the template are then cut, and the template is removed, leaving the ring in place. Such templates, however, do not prevent the ring from bunching or pleating when the implant sutures are tied off, if the sutures are not precisely placed. The removal of the sutures, which attach the annuloplasty ring to the holder, can be cumbersome and time consuming. Cutting the sutures can also cause damage to the annuloplasty ring. Care must be taken to ensure that pieces of the suture remain attached to the holder and are not left in the patient. The drag from the suture can make it difficult to remove the ring from the holder. Further, the retention sutures can be captured by the sutures used to implant the ring, thereby creating great difficulty in removing the ring from the holder.
Using conventional techniques, most valve repair procedures require a gross thoracotomy, usually in the form of a median sternotomy or right thoracotomy, to gain access into the patient's thoracic cavity. Using such open-chest techniques enables the surgeon to see the affected valve directly, and to position his or her hands within the thoracic cavity in close proximity to the exterior of the heart for manipulation of surgical instruments and introduction of an annuloplasty ring through the atriotomy for attachment within the heart. However, these invasive, open-chest procedures produce a high degree of trauma, a significant risk of complications, an extended hospital stay, and a painful recovery period for the patient.
Minimally invasive surgery (MIS) enables valve repair without opening the chest cavity. Such minimally invasive heart valve repair surgeries still require bypass, but the procedures are accomplished by means of elongated tubes or cannulas introduced through one or more small access incisions in the thorax, with the help of endoscopes and other such visualization techniques. Such minimally invasive procedures usually provide speedier recovery for the patient with less pain and bodily trauma, thereby reducing the medical costs and the overall disruption to the life of the patient. The use of a minimally invasive approach, however, introduces new complexities to surgery thus placing a greater burden on the operating surgeon. Most notably, minimally invasive approaches drastically reduce the size of the surgical field available to the surgeon for the manipulation of tissue and for the introduction of necessary surgical instruments. These complexities are especially acute in connection with heart surgery. Unlike common heart surgeries performed using a full medial sternotomy, minimally invasive heart surgery offers a surgical field that may be only as large as a resected intercostal space or a transversely cut and retracted sternum. Consequently, the introduction and proper positioning of tools, such as annuloplasty ring holders, and other such devices, becomes a great deal more complicated.
The primary barriers to widespread adoption of minimally invasive, robot assisted (MIRA) cardiac procedures are associated with increased cardiopulmonary bypass (CPB) times and increased surgical skill requirements. Current MIRA technology does not reduce the need for CPB during cardiac procedure. To the contrary bypass times associated with some MIRA cardiac procedures are actually increased. For many MIRA cardiac procedures, the increased time on CPB limits the potential benefits and leads to the exclusion of high-risk patients.
Suture management is a primary contributor to increased CPB times in MIRA cardiac procedures. Typical mitral valve repairs involve 15-20 sutures, each requiring 5-6 knots, causing suturing to consume the majority of operating time. Surgeons are typically very experienced and comfortable tying knots with their hands, but robotic technology adds another level of complexity to this task. Knot tying with surgical robots, particularly using the smaller 2-0 sutures required for mitral valve prosthesis fixation, takes considerably longer than with minimally invasive surgical instruments. The large number of required knots in annuloplasty fixation, coupled with the increased difficulty in tying the knots robotically, cause MIRA mitral valve repair to take longer than minimally invasive surgical approaches. Operating within limited space and with limited vision, it is not surprising that surgeons require more time to tie knots in MIRA surgery, despite the assistance of tele-robotic system. Furthermore, current commercial robotic surgery systems provide no force feedback from the instruments and dexterity with current minimally invasive instruments, manual or robotic, is less than optimal. Because there is no tactile sensation, the knot tying depends on visual clues as to appropriate tension and tightness.
An improved method of suture-based knotless fixation for MIRA mitral valve repair could allow surgeons all of the flexibility and precision of current techniques, while requiring less time and training to perform. Such an improvement could allow more patients to benefit more fully from the potential of MIRA cardiac surgery through increased access and reduced cost. By reducing CPB time, more patients will be candidates for MIRA cardiac procedures. Reduced CPB time will also help reduce direct surgical cost and indirect cost associated with post-surgical recovery.
One final problem associated with the annuloplasty rings of the prior art is that when such annuloplasty rings are implanted into children or adolescents the subsequent growth of the patient may render the annuloplasty ring too small, thus abnormally constricting the annulus. Follow-up surgery would be necessary to replace the originally implanted annuloplasty ring with a larger ring suitable for the current size of the patient. However, the tissue of the heart valve annulus grows into the fabric of the ring making such surgery problematic. Therefore the preservation of growth potential in the native annulus is an important issue in terms of long-term stability of valve repair procedures in children and adolescents.
What is needed, therefore, are devices and methods for carrying out heart valve repair that reduce the trauma, risks, recovery time and pain that accompany current techniques. The devices and methods should facilitate surgical intervention without the need for a gross thoracotomy. In particular, the devices and methods should enable the implantation of annuloplasty repair segments without the need for excessive additional implements.